The present invention is directed to a bicomponent structure for use as surgical drape and in waterproof apparel and equipment.
The textile industry has manufactured so-called breathable fabrics composed of a film of a polymeric material that is permeable to water vapor bonded to a textile material. The most notable and successful material that transmits water vapor therethrough is a film of microporous polytetrafluoroethylene that is adhered to a textile material. Although this product has been outstandingly successful, it is rather expensive and the pores tend to be blocked by dirt, body oils and detergents. Also, there is a need for a waterproof film having good physical properties, low cost and offering long service life. It is known that other polymers can be formed into films that have high water-vapor transmission rates and when covered with textile materials, such as nylon or poly(ethylene terephthalate), can be used to make waterproof and water vapor permeable garments. U.S. Pat. No. 4,493,870 discloses waterproof garments made of a textile material that is covered with a single layered film of a copolyetherester made from a dicarboxylic acid, an aliphatic diol and a poly(alkylene oxide) glycol wherein at least 70% of the glycol has a carbon to oxygen ratio 2.0-2.4. Such waterproof garments described therein have water vapor transmission rate values that do not depend on the film surface facing its high humidity side. The values obtained are equal when either side is exposed to the same level of humidity. Accordingly, there is a need for breathable waterproof, water vapor permeable products that transmit water vapor at a slower rate from the environment exterior to the protective product than from the interior. For example, shoes or boots fabricated with such a product having the ability to transfer moisture at a higher rate from within, to assure comfort, would keep the wearer's feet drier for a longer period of time under exterior soaking conditions than the products disclosed in U.S. Pat. No. 4,493,870. Up to the time of the present invention, the water vapor transmission rates of the water vapor permeable layers of commercially available products, e.g., raincoats, were substantially the same in either direction. Japanese Patent Application No. 50-35623, published Oct. 1, 1976, discloses a water vapor permeable product of a single layered film of a copolyetherester elastomer covered with a textile material. The teaching in the Japanese patent application suffers the same deficiencies as those found in U.S. Pat. No. 4,493,870, e.g., the water vapor permeable product transmits water vapor at the same rate from either side of the sheet or film when exposed to the same level of humidity. The present invention describes an easily processible, low cost waterproof, water vapor permeable film for use as surgical drape and in waterproof articles, e.g., garments, having maximum benefit of rapid transmission of water-vapor through the film toward the exterior, or weather side of the garment, while minimizing the transmission of water in the opposite direction, making the garment more comfortable to wear due to the increase in the water vapor transmission rate away from the wearer while protecting the wearer from water, liquid and vapor, from exterior sources.